A thrust gate consists of transverse rows of grate plates, which transverse rows overlap one another in the manner of a roof tile and are arranged so as to be alternately stationary and moveable forwards and backwards in the longitudinal direction. The moveably arranged rows of grate plates are arranged in their entirety or in groups on frames which are carried by vertical guides and the correct lateral alignment of which is determined by lateral guides. Rollers on rails are conventionally used for vertical guidance, said rails being provided with cooperating track flanges or guide strips for the purpose of lateral guidance (EP-A-378 821, FIG. 1). It is also known (op. cit., FIG. 2), for vertical guidance, to use elongate tension elements, on which the moveable grate component is pendulously suspended. In this connection, the idea arose (op. cit., FIG. 3) of arranging the tension members obliquely in opposite directions, on the assumption that this could bring about lateral guidance, although this is obviously incorrect because such an arrangement does not rule out the possibility of lateral pendulous movement, but only modifies it. Separate lateral guidance members have therefore been retained hitherto, these being subject to wear, with the result that, on the one hand, lateral guidance quality diminishes in time and, on the other hand, complicated replacement becomes necessary from time to time.
The invention avoids these disadvantages by means of the features of Claim 1 and preferably those of the subclaims. Although the invention makes use, for lateral guidance, of members which are similar to those for pendulous grate suspension, the operative principle is nevertheless different. Whereas, in pendulous vertical guidance, a grate movement in the form of an arc of a circle necessarily takes place, lateral guidance must run in a straight line. The principle of pendulous guidance is therefore fundamentally unsuitable for lateral guidance. This also applies, in particular, when, according to the invention, horizontal pendulous guides are arranged in opposition on both sides, because the circular arcs of the pendulous guides located on both sides are not identical. The invention is based on the recognition that strict guidance is not necessary over the entire guidance distance and that it is sufficient if a defined lateral position is imparted to the grate in each case at individual points along the distance of its movement. If, for example, two opposing tension elements are arranged in such a way that they in each case stand perpendicularly to the direction of movement in the middle of the distance of movement of the grate and are tensioned exactly when the moved grate component reaches its reversal points, said tension elements thus ensure that the moved grate component has, at each of the reversal points, the desired lateral position, for example lies centrally with respect to lateral boundaries. In the case of non-extendible tension elements, guidance is restricted to the reversal points or to the adjacent region. There is theoretically no guidance in between. However, the laterally acting forces which could deflect the grate out of its central position are not so high that there would necessarily be the fear that said moved grate component would depart from its tolerance range before the next opportunity for correcting its position laterally, that is to say before the next reversal point is reached. In general terms, the tension elements are dimensioned in such a way that, in the event of a lateral deflection of the moved grate component up to the limit of its tolerance range, their tensile force is zero or insufficient in part of the distance of movement and only when one reversal point or the other is approached exceeds the amount which is necessary for a lateral correcting movement of the moveable grate component. If it is taken into account that the tension elements and those parts of the grate and of the stationary arrangement which are connected to them naturally have some elasticity, this situation can also be expressed in even more general terms, in that, in the event of a lateral deflection of the grate component up to the limit of its tolerance range, the difference in the tensile force of the tension elements in part of the distance of movement is lower than the resistance opposing a lateral displacement of the moved grate component, the difference in their tensile force exceeding this resistance only when a reversal point is approached. Admittedly, the invention also includes those versions in which the deliberate dimensioning of the elasticity and length of the tension elements has the result that, in the event of a lateral deflection of the moved grate component up to the tolerance limit, a difference in tensile force sufficient for lateral correction is produced at each point along the distance of movement. However, as stated, this is not required, because it is not necessary to reckon on a sudden lateral movement of the moveable grate component which guides the latter beyond the tolerance range.
If the difference in tensile force of the tension elements fall to zero in the middle region of the distance of movement, they theoretically become slack. This does not occur in practice, however, because, on the one hand, a complete disappearance of their lateral guidance force is unlikely on account of the elasticity inherent in them and the low height of the circular arc described by their ends and, on the other hand, the extent of any slackness is so slight that it is scarcely detectable.
It goes without saying that the tension elements should be long in relation to the longitudinal distance of movement of the moved grate component, so that their circular guidance arc becomes flat. It is sufficient, in general, if the tension elements in each case run from one lateral edge of the moved grate component to a structural part adjacent to the other lateral edge, that is to say, as a rule, over the entire width of the moved grate component.
So that the points of connection of the tension elements to the grate component and to the stationary structure are not subjected to any wear, they are expediently designed as flexural joints.